Longitudinal prevalence, oocyst shedding and molecular characterisation of Eimeria species in sheep across four states in Australia

The prevalence of Eimeria in sheep in Australia has not been well described, therefore a quantitative PCR (qPCR) was developed, validated and used to study the prevalence and oocyst concentration in lamb faecal samples at three sampling periods (weaning, post-weaning and pre-slaughter) from eight farms across South Australia, New South Wales, Victoria and Western Australia. A total of 3412 faecal samples were collected from approximately 1182 lambs across the 4 states and screened for the presence of Eimeria using this qPCR at the 18S ribosomal RNA (rRNA) locus. A subset of positives was typed by sequence analysis at the 18S locus. The overall prevalence was 18.1% (95% CI 16.8-19.3%) and of the 616 positives, 118 were successfully genotyped. The prevalence of Eimeria was highest in NSW and peaked at 70% during the post-weaning period. The range of oocyst shedding per gram of faeces (g(-1)) at weaning, post-weaning and pre-slaughter overall across all states was 23-2.1×10(7), 23-1.3×10(7) and 23-2.1×10(5), respectively. Median Eimeria shedding g(-1) was higher during post-weaning (1.1×10(3)) and pre-slaughter (1.1×10(3)) than during weaning (206). The following species were identified: Eimeria crandallis, Eimeria ahsata, Eimeria ovinoidalis, Eimeria weybridgensis and Eimeria cylindrica. Of these, E. crandallis and E. ovinoidalis, the most pathogenic species in sheep were responsible for 58.5% of infections typed. This highlights a need for further research to quantify the production impacts of Eimeria in sheep.